The present invention relates to the marking of product for tracking and identification (eg., information purposes) and more particularly to using laser marked dual-coated product zones therefor.
There is a need to identify products with high quality bar codes and human-readable information without the use of an adhesive label. For example, welded tubular goods manufacturers (e.g., manufacturers of oil and gas pipeline pipe) desire to identify their products with human-readable data (e.g., heat chemistry of the source plate, pressure testing results, American Petroleum Institute (AIP) code conformation, etc.), as well as automatic identification (e.g., bar codes) for traceability and handling efficiency.
Paper labels often are unsuitable (as is the case in the aforementioned tubular goods) because they can peel off (e.g., contaminate the pipeline) and they may not be suitable for the environment (e.g., application to hot/wet/oily surfaces or pipes which will be exposed to high temperatures during subsequent coating operations). Bar codes and, to a lesser degree, the human-readable characters, require high contrast markings on products which have a wide range of background reflectivity (e.g., shiny to dull black pipe).
Heretofore, Nierenberg (U.S. Pat. No. 4,323,755) vaporizes a pattern (bar code) on glass CRTs for their identification. To improve contrast, the vaporized area can be coated first. Williams (U.S. Pat. No. 5,206,280) discloses a laser markable white pigment composition. Shimokawa (U.S. Pat. No. 4,847,181) proposes a dual layer label that can be laser marked. Gnanamuthu (U.S. Pat. No. 4,716,270) proposes a laser marking system where substrate is etched following laser marking of a label. Norris (U.S. Pat. No. 5,262,613) retrofits a mechanical engraver with a laser. Snakenborg (U.S. Pat. No. 4,946,763) proposes form a pattern in a metal stencil which is covered by a resist material containing a high concentration of metal powder. Resist material is removed by a laser beam to form the pattern. Honaker (U.S. Pat. No. 4,935,288) proposes a laser printable label having a coating of laser printable acrylic. Kiyonari (U.S. Pat. No. 5,063,137) proposes a resin composition for laser marking having an inorganic compound, like an anhydrous metal borate salt, and a resin. Kiyonari (U.S. Pat No. 5,035,983) proposes a laser marking composition containing a non-black inorganic lead compound. Azuma (U.S. Pat. No. 4,861,620) proposes a pigment layer which can be marked by a laser beam. Herren (U.S. Pat. No. 5,030,551) laser marks ceramic materials coated with a transparent layer of titanium dioxide. Gernier (U.S. Pat. No. 4,985,780) proposes a two carriage assembly for laser marking articles. Robertson (U.S. Pat. No. 5,422,167) proposes a thermally-printable, high temperature-resistant coating for marking hot bands and like metal products.
Additionally, a variety of other raw and finished goods (e.g., automobile mechanical parts, tires, etc.) require marking for identification or information purposes. Such goods may be at or below room temperature when the marking requirement arises. A system that has the flexibility to mark "hot" metal as well as lower temperature items would be welcome.